Concept design and project cost

What concept design decides

Not details. Concept design is about:

• how big the building is and what shape,
• how many storeys,
• how it sits on the plot and which way it faces,
• what the structural system is and how large the spans are,
• where the bracing elements, the utility connections and the service risers go,
• roughly which build-ups we are working with.

Most of the cost follows from these — and these are the decisions that can only be changed later at significant loss.

Bring the structural engineer in early

Especially true with this technology. If the designer knows the strengths and weaknesses of the structure at concept stage, the work goes much faster and fewer compromises are left at the end.

A few typical examples that are cheap at concept and expensive later:

The span

Half a metre less span often means a whole section size smaller — throughout, in the whole building.

The position of the bracing

The floor plan determines where the bracing wall segments go. If the plan has no continuous wall segment in the right direction, the bracing has to be solved more expensively.

The openings

Too many or badly placed openings take away the wall area available for bracing and create lintel problems.

The service risers

If the route of the large-diameter pipes is decided early, the service cavity is enough and no lining wall is needed. Service cavity.

What to fix in the concept design

• The structural concept and the main spans.
• The principle of the bracing system.
• The type of build-ups — at least enough for the wall thicknesses to be realistic.
• The design brief: what the client expects from the building. The design brief.

What is not needed yet

Connection details, exact section sizes, named manufacturers’ products. Those are the job of the detailed design, and fixing them early means fixing them on the wrong basis.

The point

Concept design is the cheapest stage and the one with most at stake. An hour of structural discussion here is worth more than a week of patching the detailed design.